package com.github.easycaptcha.utils;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferByte;
import java.io.*;

/**
 * Gif生成工具
 * Class AnimatedGifEncoder - Encodes a GIF file consisting of one or
 * more frames.
 * <pre>
 * Example:
 *    AnimatedGifEncoder e = new AnimatedGifEncoder();
 *    e.start(outputFileName);
 *    e.setDelay(1000);   // 1 frame per sec
 *    e.addFrame(image1);
 *    e.addFrame(image2);
 *    e.finish();
 * </pre>
 * No copyright asserted on the source code of this class.  May be used
 * for any purpose, however, refer to the Unisys LZW patent for restrictions
 * on use of the associated Encoder class.  Please forward any corrections
 * to questions at fmsware.com.
 */
public class GifEncoder {
  protected int width; // image size
  protected int height;
  protected Color transparent = null; // transparent color if given
  protected int transIndex;  // transparent index in color table
  protected int repeat = -1; // no repeat
  protected int delay = 0;   // frame delay (hundredths)
  protected boolean started = false; // ready to output frames
  protected OutputStream out;
  protected BufferedImage image; // current frame
  protected byte[] pixels; // BGR byte array from frame
  protected byte[] indexedPixels; // converted frame indexed to palette
  protected int colorDepth;  // number of bit planes
  protected byte[] colorTab; // RGB palette
  protected boolean[] usedEntry = new boolean[256]; // active palette entries
  protected int palSize = 7;  // color table size (bits-1)
  protected int dispose = -1; // disposal code (-1 = use default)
  protected boolean closeStream = false; // close stream when finished
  protected boolean firstFrame = true;
  protected boolean sizeSet = false; // if false, get size from first frame
  protected int sample = 10; // default sample interval for quantizer

  /**
   * Sets the delay time between each frame, or changes it
   * for subsequent frames (applies to last frame added).
   *
   * @param ms int delay time in milliseconds
   */
  public void setDelay(int ms) {
    delay = Math.round(ms / 10.0f);
  }

  /**
   * Sets the GIF frame disposal code for the last added frame
   * and any subsequent frames.  Default is 0 if no transparent
   * color has been set, otherwise 2.
   *
   * @param code int disposal code.
   */
  public void setDispose(int code) {
    if (code >= 0) {
      dispose = code;
    }
  }

  /**
   * Sets the number of times the set of GIF frames
   * should be played.  Default is 1; 0 means play
   * indefinitely.  Must be invoked before the first
   * image is added.
   *
   * @param iter int number of iterations.
   */
  public void setRepeat(int iter) {
    if (iter >= 0) {
      repeat = iter;
    }
  }

  /**
   * Sets the transparent color for the last added frame
   * and any subsequent frames.
   * Since all colors are subject to modification
   * in the quantization process, the color in the final
   * palette for each frame closest to the given color
   * becomes the transparent color for that frame.
   * May be set to null to indicate no transparent color.
   *
   * @param c Color to be treated as transparent on display.
   */
  public void setTransparent(Color c) {
    transparent = c;
  }

  /**
   * Adds next GIF frame.  The frame is not written immediately, but is
   * actually deferred until the next frame is received so that timing
   * data can be inserted.  Invoking <code>finish()</code> flushes all
   * frames.  If <code>setSize</code> was not invoked, the size of the
   * first image is used for all subsequent frames.
   *
   * @param im BufferedImage containing frame to write.
   * @return true if successful.
   */
  public boolean addFrame(BufferedImage im) {
    if ((im == null) || !started) {
      return false;
    }
    boolean ok = true;
    try {
      if (!sizeSet) {
        // use first frame's size
        setSize(im.getWidth(), im.getHeight());
      }
      image = im;
      getImagePixels(); // convert to correct format if necessary
      analyzePixels(); // build color table & map pixels
      if (firstFrame) {
        writeLSD(); // logical screen descriptior
        writePalette(); // global color table
        if (repeat >= 0) {
          // use NS app extension to indicate reps
          writeNetscapeExt();
        }
      }
      writeGraphicCtrlExt(); // write graphic control extension
      writeImageDesc(); // image descriptor
      if (!firstFrame) {
        writePalette(); // local color table
      }
      writePixels(); // encode and write pixel data
      firstFrame = false;
    } catch (IOException e) {
      ok = false;
    }

    return ok;
  }

  //added by alvaro
  public boolean outFlush() {
    boolean ok = true;
    try {
      out.flush();
      return ok;
    } catch (IOException e) {
      ok = false;
    }

    return ok;
  }

  public byte[] getFrameByteArray() {
    return ((ByteArrayOutputStream) out).toByteArray();
  }

  /**
   * Flushes any pending data and closes output file.
   * If writing to an OutputStream, the stream is not
   * closed.
   *
   * @return boolean
   */
  public boolean finish() {
    if (!started) return false;
    boolean ok = true;
    started = false;
    try {
      out.write(0x3b); // gif trailer
      out.flush();
      if (closeStream) {
        out.close();
      }
    } catch (IOException e) {
      ok = false;
    }

    return ok;
  }

  public void reset() {
    // reset for subsequent use
    transIndex = 0;
    out = null;
    image = null;
    pixels = null;
    indexedPixels = null;
    colorTab = null;
    closeStream = false;
    firstFrame = true;
  }

  /**
   * Sets frame rate in frames per second.  Equivalent to
   * <code>setDelay(1000/fps)</code>.
   *
   * @param fps float frame rate (frames per second)
   */
  public void setFrameRate(float fps) {
    if (fps != 0f) {
      delay = Math.round(100f / fps);
    }
  }

  /**
   * Sets quality of color quantization (conversion of images
   * to the maximum 256 colors allowed by the GIF specification).
   * Lower values (minimum = 1) produce better colors, but slow
   * processing significantly.  10 is the default, and produces
   * good color mapping at reasonable speeds.  Values greater
   * than 20 do not yield significant improvements in speed.
   *
   * @param quality int greater than 0.
   */
  public void setQuality(int quality) {
    if (quality < 1) quality = 1;
    sample = quality;
  }

  /**
   * Sets the GIF frame size.  The default size is the
   * size of the first frame added if this method is
   * not invoked.
   *
   * @param w int frame width.
   * @param h int frame width.
   */
  public void setSize(int w, int h) {
    if (started && !firstFrame) return;
    width = w;
    height = h;
    if (width < 1) width = 320;
    if (height < 1) height = 240;
    sizeSet = true;
  }

  /**
   * Initiates GIF file creation on the given stream.  The stream
   * is not closed automatically.
   *
   * @param os OutputStream on which GIF images are written.
   * @return false if initial write failed.
   */
  public boolean start(OutputStream os) {
    if (os == null) return false;
    boolean ok = true;
    closeStream = false;
    out = os;
    try {
      writeString("GIF89a"); // header
    } catch (IOException e) {
      ok = false;
    }
    return started = ok;
  }

  /**
   * Initiates writing of a GIF file with the specified name.
   *
   * @param file String containing output file name.
   * @return false if open or initial write failed.
   */
  public boolean start(String file) {
    boolean ok = true;
    try {
      out = new BufferedOutputStream(new FileOutputStream(file));
      ok = start(out);
      closeStream = true;
    } catch (IOException e) {
      ok = false;
    }
    return started = ok;
  }

  /**
   * Analyzes image colors and creates color map.
   */
  protected void analyzePixels() {
    int len = pixels.length;
    int nPix = len / 3;
    indexedPixels = new byte[nPix];
    Quant nq = new Quant(pixels, len, sample);
    // initialize quantizer
    colorTab = nq.process(); // create reduced palette
    // convert map from BGR to RGB
    for (int i = 0; i < colorTab.length; i += 3) {
      byte temp = colorTab[i];
      colorTab[i] = colorTab[i + 2];
      colorTab[i + 2] = temp;
      usedEntry[i / 3] = false;
    }
    // map image pixels to new palette
    int k = 0;
    for (int i = 0; i < nPix; i++) {
      int index =
          nq.map(pixels[k++] & 0xff,
              pixels[k++] & 0xff,
              pixels[k++] & 0xff);
      usedEntry[index] = true;
      indexedPixels[i] = (byte) index;
    }
    pixels = null;
    colorDepth = 8;
    palSize = 7;
    // get closest match to transparent color if specified
    if (transparent != null) {
      transIndex = findClosest(transparent);
    }
  }

  /**
   * Returns index of palette color closest to c
   *
   * @param c color
   * @return int
   */
  protected int findClosest(Color c) {
    if (colorTab == null) return -1;
    int r = c.getRed();
    int g = c.getGreen();
    int b = c.getBlue();
    int minpos = 0;
    int dmin = 256 * 256 * 256;
    int len = colorTab.length;
    for (int i = 0; i < len; ) {
      int dr = r - (colorTab[i++] & 0xff);
      int dg = g - (colorTab[i++] & 0xff);
      int db = b - (colorTab[i] & 0xff);
      int d = dr * dr + dg * dg + db * db;
      int index = i / 3;
      if (usedEntry[index] && (d < dmin)) {
        dmin = d;
        minpos = index;
      }
      i++;
    }
    return minpos;
  }

  /**
   * Extracts image pixels into byte array "pixels"
   */
  protected void getImagePixels() {
    int w = image.getWidth();
    int h = image.getHeight();
    int type = image.getType();
    if ((w != width)
        || (h != height)
        || (type != BufferedImage.TYPE_3BYTE_BGR)) {
      // create new image with right size/format
      BufferedImage temp =
          new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
      Graphics2D g = temp.createGraphics();
      g.drawImage(image, 0, 0, null);
      image = temp;
    }
    pixels = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
  }

  /**
   * Writes Graphic Control Extension
   *
   * @throws IOException IO异常
   */
  protected void writeGraphicCtrlExt() throws IOException {
    out.write(0x21); // extension introducer
    out.write(0xf9); // GCE label
    out.write(4); // data block size
    int transp, disp;
    if (transparent == null) {
      transp = 0;
      disp = 0; // dispose = no action
    } else {
      transp = 1;
      disp = 2; // force clear if using transparent color
    }
    if (dispose >= 0) {
      disp = dispose & 7; // user override
    }
    disp <<= 2;

    // packed fields
    out.write(0 | // 1:3 reserved
        disp | // 4:6 disposal
        0 | // 7   user input - 0 = none
        transp); // 8   transparency flag

    writeShort(delay); // delay x 1/100 sec
    out.write(transIndex); // transparent color index
    out.write(0); // block terminator
  }

  /**
   * Writes Image Descriptor
   *
   * @throws IOException IO异常
   */
  protected void writeImageDesc() throws IOException {
    out.write(0x2c); // image separator
    writeShort(0); // image position x,y = 0,0
    writeShort(0);
    writeShort(width); // image size
    writeShort(height);
    // packed fields
    if (firstFrame) {
      // no LCT  - GCT is used for first (or only) frame
      out.write(0);
    } else {
      // specify normal LCT
      out.write(0x80 | // 1 local color table  1=yes
          0 | // 2 interlace - 0=no
          0 | // 3 sorted - 0=no
          0 | // 4-5 reserved
          palSize); // 6-8 size of color table
    }
  }

  /**
   * Writes Logical Screen Descriptor
   *
   * @throws IOException IO异常
   */
  protected void writeLSD() throws IOException {
    // logical screen size
    writeShort(width);
    writeShort(height);
    // packed fields
    out.write((0x80 | // 1   : global color table flag = 1 (gct used)
        0x70 | // 2-4 : color resolution = 7
        0x00 | // 5   : gct sort flag = 0
        palSize)); // 6-8 : gct size

    out.write(0); // background color index
    out.write(0); // pixel aspect ratio - assume 1:1
  }

  /**
   * Writes Netscape application extension to define
   * repeat count.
   *
   * @throws IOException IO异常
   */
  protected void writeNetscapeExt() throws IOException {
    out.write(0x21); // extension introducer
    out.write(0xff); // app extension label
    out.write(11); // block size
    writeString("NETSCAPE" + "2.0"); // app id + auth code
    out.write(3); // sub-block size
    out.write(1); // loop sub-block id
    writeShort(repeat); // loop count (extra iterations, 0=repeat forever)
    out.write(0); // block terminator
  }

  /**
   * Writes color table
   *
   * @throws IOException IO异常
   */
  protected void writePalette() throws IOException {
    out.write(colorTab, 0, colorTab.length);
    int n = (3 * 256) - colorTab.length;
    for (int i = 0; i < n; i++) {
      out.write(0);
    }
  }

  /**
   * Encodes and writes pixel data
   *
   * @throws IOException IO异常
   */
  protected void writePixels() throws IOException {
    Encoder encoder = new Encoder(width, height, indexedPixels, colorDepth);
    encoder.encode(out);
  }

  /**
   * Write 16-bit value to output stream, LSB first
   *
   * @param value int
   * @throws IOException IO异常
   */
  protected void writeShort(int value) throws IOException {
    out.write(value & 0xff);
    out.write((value >> 8) & 0xff);
  }

  /**
   * Writes string to output stream
   *
   * @param s string
   * @throws IOException IO异常
   */
  protected void writeString(String s) throws IOException {
    for (int i = 0; i < s.length(); i++) {
      out.write((byte) s.charAt(i));
    }
  }
}
